OBJECTIVE: To determine if atropine can eliminate the age-related decline in outflow facility in rhesus monkeys RESULTS We determined in rhesus monkeys ages 4-24 years, that baseline outflow facility decreases by 0.0160q0.0059 l/min/mmHg/yr. The average baseline facility was ~50% higher in the youngest (ages 4-=10 years) compared to the oldest (ages 21-25 yrs). Atropine decreased facility by 25% compared to baseline in the youngest monkeys but not at all in the oldest animals. The inability of atropine to completely eliminate the age-related facility decline indicates the presence of atropine-independent, facility relevant age-dependent changes in the trabecular meshwork itself such as loss of cells or build-up of extracellular material. Similar changes could contribute to the development of elevated intraocular pressure and glaucoma in aging humans. FUTURE DIRECTIONS We will study the age-dependence of uveoscleral outflow in rhesus; another fluid outflow pathway which may be compromised during the aging process. KEY WORDS atropine, trabecular meshwork, extracellular material, glaucoma